Secondary fuel system for a supplementary fired heat recovery steam generator

ABSTRACT

A supplementary-fired heat recovery steam generator having a secondary source of liquid fuel and where superheated steam from the steam generator, or an external source, is used to vaporize the liquid fuel which has been atomized in a vaporization chamber.

United States Patent Inventor Salvatore S. Tramuta North Windham, Maine Applt No. 799,186

Filed Feb. 14, 1969 Patented Feb. 9, 1971 Assignee General Electric Company a corporation of New York SECONDARY FUEL SYSTEM FOR A SUPPLEMENTARY FIRED HEAT REcovERY S EAM-QE BATQB 2 Claims, l l )rawing Fig.

US. Cl 122/7 Int. Cl F221) l/l8 Field ofSearch 158/11 (Digest); 431/1 1, 211, 285; 122/7 FAA/1 E11 [56] References Cited Primary Examiner-Kenneth W. Sprague Attorneys-William C. Crutcher, Frank L. Neuhauser, Oscar B. Waddell and Melvin M. Goldenberg ABSTRACT: A supplementary-fired heat recovery steam generator having a secondary source of liquid fuel and where superheated steam from the steam generator, or an external source, is used to vaporize the liquid fuel which has been atomized in a vaporization chamber.

PATENTEUFEB 9am 3561.405

INVENTOR SALVATORE S. TRAMUTA,

BIA/(J- aM/M HIS ATTORNEY.

BACKGROUND OF THElNVENTlON My invention relates to a supplementaryfired heat recovery steam generator and more particularly to one which has a .secondary source of liquid fuel. Prior to my invention, supplementary-fired heat recovery steam generators had a single pri- 7 mary source of fuel to mix with the oxygen-containing exhaust gases from a gas turbine. This fuel was of the gaseous type which permitted easy mixing with the exhaust gases and comvbination thereafter in a burner placed in the exhaust gas stream. The combination process increases the temperature of the gas turbine exhaust gases which allows a greater heat exchange rate in the steam generator and the consequent production of more steam.

Due to limited amounts of gaseous fuel in some cases, it became necessary to provide a secondary source of fuel in a simple and economical way. A liquid supply is easy to store, but since the bumerused in the steam generator is adapted to gaseous fuels, it is necessary to vaporize the liquid fuel before entering the burner. According y, the invention has as its objective the improvement in reliability of the supplementaryfired heat recovery steam generator by providing a secondary source of vaporized liquid fuel to burn with the gas turbine exhaust.

Other objects, advantages and features of the present invention will become apparent from the following description of one embodiment thereof when taken in connection with th accompanying drawing.

SUMMARY or THE-INVENTION liquid fuel which is preheated by preheater element 28 and pressurized by means of a pressure source 29 such as a gas bottle. Pressure gage 30 and temperature gage 31 sense those respective properties within fuel supply 27. When the secondary fuel supply 27 is being used, i.e., when the primary source of fuel 36 is cut off, the heated liquid fuel under pressure'flows through line 32 into vaporizing chamber 19. The flow in line 32 is controlled by valve 33.

The operation of the invention is as follows. Primary source of fuel 36 of the gaseous type is usually readily available. Under normal operating conditions;-valves I8 and 33 are closed so secondary fuel supply 27 is inoperative and so that secondary that no superheated steam is drawn into line 17. In such a condition valve 37 is open-so as to allow the gaseous fuel to flow through line 38 which runs from primary source 36 to burner 8 where combustion with the gas turbine exhaust gases takes place.

Suitable means of controlling the rate of fuel flow, hence steam generation, are not shown here, since they are not material to the present invention.

If for any reason primary source of fuel 36 is cut off and it is I still desired to have steam generator 7 in an operative condition, valve 37 is closed and valves 18 and 33 are opened thus v allowing the secondary fuel system to operate without requir- Briefly stated, my invention is practiced in one form by I providing the supplementary-fired "heat recovery steam generator ina combined steam and gas turbine cycle with a pressurized secondary liquid fuel supply which is atomized and then vaporized in a vaporizing chamber by superheated steam from the steam generator or an external source. Part of the superheated steam is allowed to vaporize the liquid fuel in the vaporizing chamber and the steam-.fuel mixture is then fed into a burner to be combined with the oxygen-containing exhaust gases from the gas turbine. DRAWING ing a shutdown of the steam generator. In this operating condition, superheated steam is allowed to enter vaporizing chamber 19 where it meets the preheated liquid fuel under pressure which has been atomized by atomizer 20. The finely atomized liquid fuel immediately .vaporizes upon contacting the superheated steam; This steam-fuel mixture exists through steam fuel outlet 23 into line 39. Since valve 37 has been closed, the steam-fuel mixture flows through line 38 to burner 8 where it provides the fuel to combine with the oxygen containing gas turbine exhaust. Upon combustion, the resulting hotter gases pass over superheater 9 which produces more su- The single figure of the drawingis a simplified schematic diagram of the present invention-DESCRIPTION v V I 7 Referring to the drawing, a detailed description willnow be made. A gas turbine is generally shown at l which consists of a compressor 2 burners 3, and turbine 4. The combustion supportable exhaust gases from gas turbine 1 are channeled through exhaust line 5 and into the inlet conduit 6 of the supplementary-fired heat recovery steam generator which isgenerally indicated as 7. The steam generator, which is known to the art, consists of burner 8, superheater 9, evaporator 10, and economizer ll disposed in an upstream to downstream relationship with respect to the exhaust gas flow within conduit or stack l2. A suitable burner configuration for a supplementary fired system is shown in abandoned application Ser.

No.644,383 filed in the names of'R.A. Lambert and D.L. Murray on June 7, I967 and assigned to the present assignee. External to stack 12 but forming a necessary part of steam generator 7 is steam drum 13 with related recirculation pump As superheated steam is generated in superheater 9, it flows through outlet line 15 and into line 16 which leads to the steams point of use. Bleed line l 7draws a portionof the superheated steam from line 16 depending on the position of valve 18 which is disposed in bleed line 17. Valve 18 is a control valve which controls the amount of steam that flows into vaporizing chamber 19.. vaporizing chamber 19 consists of atomizer 20, steam inlet 21, fuel inlet 22, and steam-fuel outlet 23. Atomizer 20 can be of the type which is a perforated tube disposed coaxially within vaporizing chamber 19. Pressure gage 24 and temperature gage 25 are disposed in the steam inlet line 21 in order to sense those properties of the perheated steam in order to continue the cycle when the secondary source of fuel is being utilized.

It will be appreciated that a supplementary-fired heat recovery steam generator with a secondary source of liquid fuel which is vaporized by superheated steam from the steamgenerator has been described; This offers a secondary fuel supply in emergencies at the lowest'cost, thus providing an overall greater reliability. The steam acts as an inert gas carrier and can also be used to clean the burner system.

of ,hot combustion-supporting exhaust gases, the improvement comprising:

a primary source of gaseous fuel communicating with said burner;

a vaporizing chamber communicating with said burner;

a secondary source of liquid fuel communicating withsaid vaporizing chamber;

a bleeder steam line from said superheater communicating withsaid vaporizing chamber, thereby providing a source of high temperature steam to vaporize the liquid fuel; arid means to preheat said secondary source of liquid fuel.

2. A heat recovery steam generator of the type as defined in claim 1 where said vaporizing chamber contains a perforated pipe connected to said secondary fuel source and disposed coaxially within said chamber in order to atomize the liquid fuel under pressure. 

1. In a supplementary-fired heat recovery stEam generator system of the type comprising a burner adapted to utilize gaseous fuel, a superheater, and an evaporator disposed in the path of hot combustion-supporting exhaust gases, the improvement comprising: a primary source of gaseous fuel communicating with said burner; a vaporizing chamber communicating with said burner; a secondary source of liquid fuel communicating with said vaporizing chamber; a bleeder steam line from said superheater communicating with said vaporizing chamber, thereby providing a source of high temperature steam to vaporize the liquid fuel; and means to preheat said secondary source of liquid fuel.
 2. A heat recovery steam generator of the type as defined in claim 1 where said vaporizing chamber contains a perforated pipe connected to said secondary fuel source and disposed coaxially within said chamber in order to atomize the liquid fuel under pressure. 